In the catalysis field, “Raney method” is one of methods for preparing an active metal catalyst, and such a method comprises: i) preparing a two- or more-component alloy containing an active metal at first, and ii) leaching out at least one metal component, leaving a metal having a high catalytic activity and a porous structure. Step ii) is also referred to as “activation”. For example, M. Raney invents at the earliest a Raney nickel catalyst (Industrial and Engineering Chemistry, 1940, Vol. 32, 1199), which catalyst is prepared as follows: a nickel-aluminum alloy is prepared at first, the aluminum element in the alloy is then dissolved with a strong base solution, leaving nickel metal having a porous structure and a very high catalytic activity.
Raney catalysts include Raney nickel catalysts, Raney cobalt catalysts, Raney copper catalysts and the like, among which Raney nickel catalysts are the most common. Raney nickel catalysts are usually in the form of powder and flammable so that their handling is inconvenient. Thus, Raney nickel catalysts are mostly used in small-scale catalytic hydrogenation reaction in the fine chemical field, but cannot be used in a conventional fixed bed reaction.
In order to expand the application field of the Raney nickel catalysts, forming them into a shape by a certain method, especially into a fixed bed catalyst, is a research direction drawing many attentions in recent years.
Patent application CN1557918 discloses a shaped Raney nickel catalyst and its preparation, with the catalyst being prepared by directly kneading an alloy powder consisting of Al and one or more of Ni, Co, Cu and Fe, an inorganic matter such as pseudoboehmite as a binder, and a natural or synthetic organic matter such as Sesbania cannabina powder or carboxymethyl cellulose as a pore template agent, molding, calcining, and activating with a caustic solution. The catalyst has a certain shape and strength, and may be used as a fixed bed catalyst.
U.S. Pat. No. 5,536,694 discloses a shaped, activated Raney metal fixed bed catalyst, which is obtained by molding at least one catalyst alloy powder, a pure Raney method metal powder as a binder, a shaping aid, and a pore-producer, followed by calcination and activation with a caustic solution.
U.S. Pat. No. 4,826,799 discloses a method for preparing a shaped Raney catalyst, comprising sufficiently uniformly mixing a Raney alloy with a polymer, a mineral oil, etc. at a certain temperature, shaping the resultant mixture by a method such as extrusion, then burning off the polymer or remaining the polymer, and finally leaching out metallic aluminum with a strong base solution to afford an activated catalyst. This method can easily afford a shaped catalyst. However, if the polymer is remained, then due to the wrapping or covering of the Raney alloy by the polymer during the shaping, there are less catalytically active sites so that the catalyst has a relatively low or even no catalytic activity; if the polymer is burned off by a high-temperature calcination, then quite a number of particles will be sintered so that the activity is low.
Therefore, there is still a need to a Raney catalyst which has a high activity, a good selectivity and a good particle strength and can be used in fixed beds.